Method for forming substrate with gold surface

1:

• A method for forming a substrate having a gold surface for surface-enhanced Raman scattering (SERS), comprising:
• forming a monolayer assembly on a first glass substrate by:
• dropping a 200-400 μL aliquot of a colloid of gold nanoparticles onto the first glass substrate to form a film;
• placing a second glass substrate onto the film, wherein the colloid is disposed between the first and second glass substrates and the first and second glass substrates are spaced 0.1-2 mm apart;
• irradiating the colloid disposed between the first and second glass substrates with infrared light to evaporate the solvent to form the monolayer assembly of gold nanoparticles, wherein the monolayer assembly of gold nanoparticles includes a plurality of strips of gold nanoparticles spaced 25 μm apart and wherein each gold nanoparticle of the plurality of strips of gold nanoparticles is adjacent to at least six other gold nanoparticles;
• dissolving the compound in water to form a solution;
• adding the first glass substrate at least partially coated with the gold nanoparticles to the solution to form a mixture;
• wherein the gold nanoparticles are in a monolayer assembly on the first glass substrate;
• wherein the gold nanoparticles are 20-200 nm in size;
• wherein a surface of the gold nanoparticles is not functionalized with an outer shell;
• wherein the monolayer assembly is formed without a surfactant or linker;
• removing the first glass substrate from the mixture and washing with water to form a SERS sample having at least a portion of molecules of the compound adsorbed to the gold nanoparticles on the first glass substrate;
• and
• recording a SERS spectrum of the SERS sample;
• wherein the SERS signal of the SERS spectrum is higher than a SERS signal of a SERS spectrum of the compound on a different substrate without the gold nanoparticles.